<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="vue.js"></script>
    <title>Document</title>
</head>
<body>
    <main id="app">
        <h1>{{letters | bigLetters}}</h1>
        <h1>{{letters | smallLetters}}</h1>
    </main>
    <script>
        var vue=new Vue({
            el:'#app',
            data:{
                letters:'bciweHJIHBnijOI'
            },
            filters:{
                bigLetters:function(value){
                    if(value==value.toLowerCase()){
                        return 
                    }
                    return value.toLowerCase()
                },
                smallLetters:function(value){
                    if(value==value.toUpperCase()){
                        return
                    }
                    return value.toUpperCase()
                }
            }
        })
    </script>
</body>
</html>